*NOTE: Federal Aid Projects require US Code of Federal Regulations 23CFR635.410, the "Buy American Steel and Iron Regulation" be followed. This is stated in the Contract Special Provisions (1601) SOURCE OF SUPPLY AND QUALITY.The iron detectable warning surfaces on this list may or may not be made in the USA.It is the contractors responsibility to ascertain the country of origin before installing or purchasing detectable warning surfaces, if the above regulation applies.At this time MnDOT is only allowing cast iron detectable warning surfaces.Approval Status is based upon the individual foundry and the submitted pattern. A change in the foundry or pattern voids the approvaland a new sample must be submitted.